WOODSTOCK, Ont. — A former Ontario nurse angry with her career and personal life believed she was an instrument of God as she used insulin to kill vulnerable seniors in her care over the course of nearly a decade.

About seven months after her arrest last fall, Elizabeth Wettlaufer pleaded guilty Thursday to eight counts of first-degree murder, four counts of attempted murder and two counts of aggravated assault.

The crimes — which took place in three Ontario long-term care facilities and at a private home — make Wettlaufer one of Canada's most prolific serial killers.

Emotional family and friends of her victims packed a courtroom in Woodstock, Ont., as the 49-year-old quietly said the word "guilty'' 14 times before a judge and admitted she used insulin in every case.

Prosecutors then laid out the details of each incident in an agreed statement of facts that included chilling revelations Wettlaufer made to police.

In Aug. 11, 2007, Wettlaufer deliberately injected James Silcox, an 84-year-old man with diabetes and Alzheimer's disease, with insulin, "hoping he would die,'' the Crown said.

"It was his time to go because of the way he acted,'' the former nurse told police, according to the agreed statement of facts.

Silcox was later found without vital signs by a personal support worker, court heard. That was Wettlaufer's first ``successful'' kill after two previous attempts failed.

Wettlaufer told investigators that afterwards, she felt "like a pressure had been relieved from me, like pressure had been relieved from my emotions.''

There were religious undertones to many of the killings, court heard, and in some cases, there was no motive other than "returning them to god,'' court heard.

"I honestly felt that God wanted to use me,'' she told investigators at one point about her efforts to kill one elderly woman.

Wettlaufer says she comforted victims' families

Wettlaufer would even comfort some of her victims' families. In one incident, court heard that she hugged the niece of a 90-year-old woman she had murdered.

The former nurse may have gotten away with the killings if she kept quiet. But, court heard, she told many people about killing patients with insulin, a practice that peaked shortly before she admitted herself to a psychiatric hospital in Toronto last September.

There she repeatedly confessed to the killings to doctors and staff, who told police.

"She insisted she wanted to be treated seriously,'' said Crown attorney Fraser Kelly.

She jumped at the chance for an interview with Toronto police, where she confessed again. Then she told the story, "with great recall and in great detail,'' to Woodstock police, Kelly said.

Some family members of Wettlaufer's victims broke down in the courtroom as the proceedings unfolded.

Susan Horvath, whose father was killed in 2014, called Wettlaufer a monster.

Susan Horvath, daughter of victim Arpad Horvath, holds a photo of her father from his 70th birthday as she speaks to the media outside the court house where Elizabeth Wettlaufer made an appearance in Woodstock, Ont. on April 21, 2017. (Photo: Dave Chidley/CP)

Horvath said she could not forgive the former nurse and called for better oversight at the province's long-term care facilities.

"`I don't want my dad's death, and everybody's death, to just be wasted,'' she said. "Let's make a change.''

Records from the College of Nurses of Ontario show Wettlaufer was first registered as a nurse in August 1995 but resigned Sept. 30, 2016, and is no longer a registered nurse. She also faces a disciplinary hearing with the college, court heard.